Reclaimed joint sheet

ABSTRACT

A reclaimed joint sheet used as a gasket or packing member for automobiles, ships and the like consists of a first layer of a joint sheet made from a given composition, a second layer of a joint sheet made by mixing finely pulverized pieces of the joint sheet after the punching out of the joint sheet having a given particle size with a composition for the formation of the joint sheet, and a third layer of a joint sheet containing the same components as the first layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a reclaimed joint sheet among joint sheetsused as a material of a gasket or a packing for automobiles, ships,various machinery and equipment and the like.

2. Description of the Related Art

The joint sheet is produced by inserting a composition for the formationof the joint sheet comprising inorganic fibers or organic fibers or amixture thereof, a rubber material, rubber chemicals and a fillerbetween a pair of a hot roll and a cold roll to heat and roll thecomposition, laminating the composition on the hot roll in the form of asheet, and then peeling off the laminated sheet from the hot roll. Next,the resulting sheet is punched out in a shape to be used as a packing.

However, when the joint sheet is punched out in form of a packing, agreat amount of scraps corresponding to 60-70% of the joint sheet iscreated, so that there are problems that the material yield is low andthe cost is increased.

SUMMARY OF THE INVENTION

It is, therefore, an object of the invention to solve the aforementionedproblems and to provide a reclaimed joint sheet.

According to a first aspect of the invention, a composition for theformation of the joint sheet comprising inorganic fibers or organicfibers or a mixture thereof, a rubber material, rubber chemicals and afiller is kneaded and inserted between a pair of a hot roll and a coldroll to heat and roll the composition, whereupon the composition isheated and rolled to laminate on the hot roll in the form of a sheet,and then the laminated sheet is peeled off from the hot roll to obtain ajoint sheet, which is punched out in a shape to be used to form apacking, during which the punched pieces of the joint sheet are finelypulverized into particles having a particle size of not more than 1.4 mmby means of a grinder and added to the same composition for theformation of the joint sheet as mentioned above in an amount of not morethan 50 weight % to produce a reclaimed joint sheet in the same manneras mentioned above.

According to a second aspect of the invention, a reclaimed joint sheetis constituted by a first layer of a joint sheet made from a compositionfor the formation of the joint sheet comprising inorganic fibers ororganic fibers or a mixture thereof, a rubber material, rubber chemicalsand a filler, a second layer of a joint sheet made by finely pulverizingpunched pieces obtained after the punching out of the above joint sheetinto a shape to be used as a packing into particles having a particlesize of not more than 1.4 mm by means of a grinder and then adding thesame to a composition for the formation of the joint sheet in an amountof not more than 50 weight %, and a third layer of the same joint sheetcomponents as the first layer.

The term "punched pieces" used herein includes redundant scraps of thecomposition in the formation of the sheet, defective goods, a fragmentat the cutting step in addition to pieces produced in the punching ofthe sheet.

As mentioned above, according to the invention, since pieces of thejoint sheet produced in the conventional punching of the joint sheet inthe form of a packing can be reused, not only is the material yieldimproved and the cost decreased, but also industrial wastes aredecreased. Furthermore, each of the first and third layers in thereclaimed joint sheet according to the invention as an outer face ismade from a joint sheet not including the punched pieces of the jointsheet, so that the seal surface becomes smooth and even and consequentlysufficient sealing performance can be developed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein:

FIG. 1 is a schematic view illustrating a method of producing a jointsheet;

FIG. 2 is a partially enlarged sectional view of the conventional sheetlaminate laminated on a hot roll;

FIG. 3 is a partially enlarged sectional view illustrating an embodimentof the reclaimed joint sheet according to invention laminated on the hotroll; and

FIG. 4 is a graph showing a relation between an amount of punched piecesadded and a tensile strength of the resulting reclaimed sheet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the invention, a composition 1 for the formation of thejoint sheet comprising inorganic fibers or organic fibers or a mixturethereof, a rubber material, rubber chemicals and a filler, which iskneaded, for example, in an agitator (see FIG. 1), is inserted between apair of a hot roll 2 and a cold roll 3, whereupon the composition 1 isheated and rolled to laminate the composition 1 on the hot roll 2 in theform of a sheet 4. The laminated sheet 4 is peeled off from the hot rolland punched out into a shape to be used as a packing. Then, the punchedpieces of the joint sheet are finely pulverized into particles having aparticle size of not more than 1.4 mm by means of a grinder and added toa composition for the formation of the joint sheet as mentioned above inan amount of not more than 50 weight % to produce a reclaimed jointsheet.

In FIG. 1, numeral 5 is a hood for recovering a solvent such as tolueneor the like disposed above the cold roll 3, and numeral 6 a solventrecovering vessel. FIG. 2 is a partially enlarged sectional view of theconventional sheet laminate 4 laminated on the hot roll 2, in whichnumeral 4a is a first layer of the sheet laminate and numeral 4b asecond layer thereof. FIG. 3 is a partially enlarged sectional view of areclaimed joint sheet 7 of three layer construction according to theinvention laminated on the hot roll 3, in which numeral 7a is a firstlayer, numeral 7b a second layer and numeral 7c a third layer.

As the inorganic fiber, use may be made of glass fiber, rock wool,various ceramic fibers, carbon fiber and metal fiber.

As the organic fiber, use may be made of aromatic polyamide fiber,fibrillated aromatic polyamide fiber, polyamide fiber, polyolefin fiberand the like.

These inorganic fibers and organic fibers may be used alone or inadmixture thereof. In case of the mixture of the inorganic fiber andorganic fiber, the mixing ratio of the inorganic fiber to the organicfiber is generally about 1:1-4:1 in weight ratio. Furthermore, thesefibers are compounded into the joint sheet in an amount of about 10-60weight %.

As the rubber material, use may be made of nitrile rubber (NBR),styrene-butadiene rubber (SBR), isoprene rubber (IR), chloroprene rubber(CR), ethylene-propylene rubber (EPM), fluororubber (FPM), siliconerubber (SI) and the like. The rubber material is compounded into thejoint sheet in an amount of about 10-30 weight %.

As the rubber chemicals, there are used a vulcanizing agent such assulfur, zinc oxide, magnesium oxide or the like, and a vulcanizationaccelerator such as thiazole compound, polyamine compound, sulfenamidecompound, guanidine compound or the like. The rubber chemicals arecompounded into the joint sheet in an amount of about 0.5-10 weight %.

As the filler, use may be made of clay, talc, barium sulfate, sodiumbicarbonate, graphite, calcium carbonate, carbon black, diatomaceousearth, mica, aluminum sulfate, alumina hydrate, magnesium carbonate andthe like. The filler is compounded into the joint sheet in an amount ofabout 10-70 weight %.

An example of a first composition for the first layer 4a shown in FIG. 2is shown as follows.

    ______________________________________    Fibrillated aromatic polyamide fiber                        15 weight %    NBR                 12 weight %    Rubber chemicals     3 weight %    Filler              70 weight %    Toluene             0.4 l per 1 kg of the above                        mentioned mixture    ______________________________________

An example of a second composition for the second layer 4b shown in FIG.2 is shown as follows.

    ______________________________________    Fibrillated aromatic polyamide fiber                        10 weight %    Glass fiber         10 weight %    NBR                 18 weight %    Rubber chemicals     2 weight %    Filler              60 weight %    Toluene             0.4 l per 1 kg of the above                        mentioned mixture    ______________________________________

The above first and second compositions are used to produce a jointsheet as follows. At first, the first composition is inserted between ahot roll 2 heated to 120°-150° C. and a cold roll 3 maintained at30°-50° C. When a thickness of the first composition reaches to 10-20%of a thickness of a desired sheet, the second composition is added ontothe first composition to form a sheet laminate shown in FIG. 2. In thiscase, a pressure between the rolls 2, 3 is maintained at about 20-40bar. Thereafter, the sheet laminate is subjected to a vulcanizationtreatment at a temperature of 100°-150° C. in a drying furnace for 30-60minutes. The thus obtained joint sheet is subjected to a punching andused as a packing.

According to the invention, the punched pieces of the above joint sheetare charged into a grinder, where they are finely pulverized at 5000 rpminto particles having a particle size of not more than 1.4 mm and addedto the a composition as mentioned above for reuse.

In the reclaimed joint sheet according to the invention, the amount ofthe punched pieces added is practically suitable to be not more than 50weight %. An example of a composition for the formation of the reclaimedjoint sheet containing 10 weight %, 30 weight % or 50 weight % of thepunched pieces is shown as follows.

    ______________________________________    Punched pieces                10 weight %                           30 weight %                                      50 weight %    Fibrillated aromatic                18 weight %                           6.5 weight %                                      4 weight %    polyamide fiber    Glass fiber 18 weight %                           6.5 weight %                                      4 weight %    NBR         18 weight %                           18 weight %                                      18 weight %    Rubber chemicals                2 weight % 2 weight % 2 weight %    Filler      52 weight %                           37 weight %                                      22 weight %    Toluene     0.4 l per 1 kg of the above mentioned                mixture    ______________________________________

Moreover, an embodiment of the reclaimed joint sheet 7 shown in FIG. 3is shown as follows.

    ______________________________________               first layer                          second layer                                      third layer    Layer      (7a)       (7b)        (7c)    ______________________________________    Fibrillated               15 weight %                          4.5 weight %                                      10 weight %    aromatic    polyamide fiber    Glass fiber               --         4.5 weight %                                      --    NBR        12 weight %                          10.5 weight %                                      18 weight %    Rubber chemicals                3 weight %                          1.4 weight %                                       2 weight %    Filler     70 weight %                          49.1 weight %                                      70 weight %    Punched pieces               --         30 weight % --    Toluene    0.4 l per 1 kg of the above mentioned               mixture    ______________________________________

The above compositions are used to produce a reclaimed joint sheet asfollows. At first, the composition for the first layer 7a is insertedbetween the hot roll 2 heated to 120°-150° C. and the cold roll 3maintained at 30°-50° C. When a thickness of the composition reaches to10-20% of a thickness of a desired sheet, the composition for the secondlayer 7b is inserted between the hot roll and the cold roll. When athickness of the composition on the first layer reaches to 70-80% of thethickness of the desired sheet, the composition for the third layer 7cis inserted between the hot roll and the cold roll to form a reclaimedjoint sheet. In this case, a pressure between the rolls 2, 3 ismaintained at about 20-40 bar. Thereafter, the sheet laminate issubjected to a vulcanization treatment at a temperature of 100°-150° C.in a drying furnace for 30-60 minutes.

In the present invention, the reason why the particle size in the finepulverization of the punched pieces is limited to not more than 1.4 mmis due to the fact that when the particle size exceeds 1.4 mm, theparticle size as an additive becomes too coarse and lower the quality ofthe reclaimed joint sheet. Further, the reason why the amount of thepunched pieces added is limited to not more than 50 weight % is due tothe fact that when the amount exceeds 50 weight %, the quality of thereclaimed joint sheet is degraded. That is, when the punched pieces areadded in an amount of more than 50 weight %, as shown in FIG. 4, theadhesion of the composition to the cold roll is caused in the formationof the sheet and the quality of the resulting reclaimed joint sheet isfrequently degraded.

As mentioned above, according to the invention, the punched pieces ofthe joint sheet after the punching of the joint sheet as a packing canbe reused, so that not only is the material yield improved and the costdecreased, but also industrial wastes are reduced. Further, each of thefirst and third layers in the reclaimed joint sheet according to theinvention is made from a joint sheet containing no punched pieces of thejoint sheet, so that the sealing surface of the joint sheet becomessmooth and even, and hence a sufficient sealing performance can bedeveloped.

What is claimed is:
 1. A reclaimed joint sheet consisting of first,second and third layers, with the second layer disposed between saidfirst and third layers, each said layer being made from a compositioncomprising organic or inorganic fibers or a mixture thereof, a rubbermaterial and filler, said second layer including up to 50% by weight ofparticles having a particle size of not more than 1.4 mm that have beenproduced by grinding punched pieces obtained after the punching out of asaid joint sheet to be used as a packing, said first and third layersbeing free from said particles.
 2. A reclaimed joint sheet according toclaim 1, wherein the inorganic fiber is selected from glass fiber, rockwool, ceramic fiber, carbon fiber and metal fiber, and the organic fiberis selected from aromatic polyamide fiber, fibrillated aromaticpolyamide fiber, polyamide fiber and polyolefin fiber.
 3. A reclaimedjoint sheet according to claim 1, wherein the mixture of the inorganicfiber and organic fiber has a mixing ratio of inorganic fiber to organicfiber of about 1:1-4:1 in weight ratio.
 4. A reclaimed joint sheetaccording to claim 1, wherein the joint sheet contains 10-60 weight % ofthe joint sheet as a whole, of the inorganic fibers or the organicfibers or the mixture thereof.
 5. A reclaimed joint sheet according toclaim 1, wherein the rubber material is selected from nitrile rubber,styrene-butadiene rubber, isoprene rubber, chloroprene rubber,ethylene-propylene rubber, fluororubber and silicone rubber, andcompounded into the joint sheet in an amount of 10-30 weight % of thejoint sheet as a whole.
 6. A reclaimed joint sheet according to claim 1,wherein rubber chemicals selected from a vulcanizing agent and avulcanization accelerator, are compounded into the joint sheet in anamount of 0.5-10 weight % of the joint sheet as a whole.
 7. A reclaimedjoint sheet according to claim 1, wherein the filler is selected fromclay, talc, barium sulfate, sodium bicarbonate, graphite, calciumcarbonate, carbon black, diatomaceous earth, mica, aluminum sulfate,alumina hydrate and magnesium carbonate, and compounded into the jointsheet in an amount of 10-70 weight % of the joint sheet as a whole.